1. Field of the Invention
The present invention relates to a printing head device of a dot-impact type printer and, particularly, to a printing head capable of being miniaturized.
2. Description of the Related Art
In a conventional dot-impact type printer, a printing head having a plurality of printing wires and a drive mechanism for driving the printing wires is put in a facing relation to a recording sheet through, for example, an ink ribbon and prints a dot pattern of such as characters on the recording sheet by selectively driving the printing wires while the head is running. FIG. 12 is a cross section of a typical conventional printing head and FIG. 13 is a plan view thereof showing an arrangement of printing elements fixed in the printing head. The printing head shown in FIG. 12 includes the printing elements 80 shown in FIG. 14 in a printing head housing 81 and arranged in an annular region as shown in FIG. 13. Each printing element 80 includes a printing wire 82, a leaf spring 83 for driving the printing wire, an armature 84, a drive coil 85, a core 86 and a yoke 87. The printing wire 82 is fixedly secured to a top end of the leaf spring 83 and has a top end which can protrude through a guide 88 provided in a top end of the printing head. The armature 84 is fixedly secured to the leaf spring 83 which, in turn, is fixedly secured in between the printing head housing 81 and the core 86. The drive coil 85 is wound on the core 86 and can be selectively driven according to a dot print signal.
When magnetic flux generated by a current flowing through the coil 85 passes through a magnetic circuit constituted with the armature 84, the core 86 and the yoke 87, the armature 84 is attracted to the core 86. Therefore, the top end of the printing wire 82 collides with the ink ribbon and the recording sheet (which are not shown) to print the latter.
In such conventional printing head, however, the magnetic circuit must be provided every printing wire, causing a miniaturization of the printing head to be very difficult.